1. Field of the Invention
While the ability to manipulate bacterial and mammalian cells by hybrid DNA technology has been available for almost a decade, only in 1983 was it first reported that successful expression of an exogenous gene was achieved in a plant cell. Plants have a highly complex genome and differ in numerous ways from both bacterial and mammalian genes. Therefore, while as a first approximation, one may extrapolate from the experience with other species, the relevance of such experience must be determined by experimentation.
In order to be able to successfully modify plant cells, it will be necessary to develop a large number of different systems for introducing the exogenous DNA into the plant cell, for directing, as appropriate, the introduced DNA either randomly or to particular genomic sites, to provide for constitutive or regulated expression and, as appropriate, to provide for transport of the product to an appropriate site. Toward this end, it will be necessary to develop a wide variety of regulatory signals involved with replication, transcription, translation, integration, and the like. To varying degrees; these regulatory signals will have general application across species or be species-specific, will be associated with specific stages of plant growth, or be subject to external control. To that extent, it will be necessary to develop a wide spectrum of regulatory sequences to allow for expression under predetermined conditions.
In addition, different systems may be required for the introduction of nucleic acid into plant cells to obtain reasonable efficiencies of transformation and functioning of the nucleic acid. In many instances, such as the tumor inducing plasmids and viruses, the vectors have found limited utilization in their range of hosts. Therefore, different transformation and replication systems may be required for different plant species.
2. Description of the Prior Art
Lack of transformation by Agrobacterium of soybean is reported by DeCleene and DeLey, The Botanical Review (1976) 42:389-466. Encouraging results in the transformation (Pederson et al., Plant Cell Repts. (1983) 2:201-204 and Hood et al., Bio/Technology (1984) 2:702-708) and regeneration (Christianson et al., Science (1983) 222:632-634) of soybean have recently been reported. A light inducible soybean SSU gene (small subunit SSU) of ribulose-1,5-bisphosphate-carboxylase (RuBP-carboxylase) is reported by Berry-Lowe et al., J. Mol. Appln. Gen. (1982) 1:483-498. Sequences 5xe2x80x2 to pSSU gene were recently shown to direct foreign gene expression in a light-inducible manner when transferred into tobacco callus (Herrera-Estrella et al., Nature (1984) 310:115-120).
Novel methods and DNA constructs are provided for transforming plants employing T-DNA and a Ti- or Ri-plasmid for heterologous DNA introduction and integration into the plant genome. Transformation without gall formation of plant cells which have historically not been Agrobacterium hosts is achieved with successful expression of the heterologous DNA.